Tube plug for plugging a tube

ABSTRACT

A fastener structure for fastening together a plurality of members, such as the plurality of members comprising a tube plug, and a method for plugging an opening in a solid member, which may be a tube, for preventing the flow of fluid through the opening in a solid member or through the tube, such as a nuclear steam generator tube, comprises a first member, such as a shell, a second member, such as bolt structure, and locking structure. A deformable tab portion of the locking structure may have an undercut positioned so that when the second member is installed within the first member, a first surface of the undercut is bent toward a second surface of the undercut thereby plastically deforming the tab portion into a recess in at least one of the first and the second members for automatically securing together the plurality of members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the fastening of a plurality of memberstogether and, more particularly, to a tube plug and method for plugginga heat exchanger tube in a nuclear steam generator.

2. Description of the Prior Art

In tube-type heat exchangers, a first fluid flows through the tubes ofthe heat exchanger while a second fluid surrounds the outside of thetubes such that heat exchange occurs between the two fluids.Occasionally, one of the tubes can become defective such that a leakeither is impending or occurs therein which allows the two fluids tomingle. When this occurs, it is sometimes necessary to plug the tube sothat the fluid does not flow through the tube thereby preventing leakagefrom the tube.

In nuclear reactor power plants, the tube-type heat exchangers arecommonly referred to as steam generators. When a defect occurs in thetubes of a nuclear steam generator that allows the primary fluid in thetubes to mingle with the secondary fluid outside of the tubes, a moresignificant problem arises. Not only does this situation create anineffective heat exchanger, but it also creates a radioactivecontamination problem. Since the fluid flowing in the tubes of a nuclearsteam generator may contain some radioactivity, it is important that itnot be allowed to leak from the tubes and possibly contaminate the fluidsurrounding the tubes and the equipment which it contacts. Therefore,when the possibility of a leak occurs in a nuclear steam generator heatexchange tube, the heat exchange tube is plugged so that the primaryfluid is not permitted to flow through the tube.

There are several kinds of mechanical plugs that can be used to plugheat exchange tubes. One such device used to plug heat exchange tubes innuclear steam generators is disclosed in U.S. Pat. No. 4,982,763 issuedJan. 8, 1991 to Klahn entitled "Plug Retainer". The plug retainer forretaining a tube plug comprises a locking cup having a bore therethroughand an externally threaded lower portion adapted to be threadablyreceived in the open threaded end of the tube plug and a cap screwhaving a threaded shank threadably receivable in the threaded mandrel ofthe tube plug. The locking cup is crimped onto the cap screw by the useof flutes on the cap screw head. However, utilization of the locking cuprequires the additional steps of threading the locking cup into the openthreaded end of the tube plug and of crimping the locking cup into theflutes of the cap screw.

Another type of mechanical plug is disclosed in co-pending applicationSer. No. 07/439,118 filed Nov. 20, 1989 by Haberman et al. and assignedto the assignee of the present invention. The tube plug for plugging atube to prevent flow through the tube comprises a shell, an expandermember, and a sealing member to seal the chamber defined by the shell.To lock or fasten the sealing member to the shell to prevent the sealingmember and shell from separating, the sealing member and shell arewelded together. The installation of the sealing member into the shellseals the open end of the shell to prevent coolant from entering thechamber of the shell and exerting pressure on the plug wall, andoccupies space within the chamber of the shell to reduce the possibilityof residual stresses within the plug wall. Although the tube plugsuccessfully plugs tubes, welding the sealing member and the shelltogether requires the additional steps of welding and of inspection ofthe weld during the installation of the tube plug into the tube. Also,if the shell of the tube plug has been recessed a distance into thetube, the sealing member cannot be welded to the shell, and thereforethe sealing member and shell cannot be locked or fastened together bywelding.

Another type of mechanical plug is disclosed in co-pending applicationSer. No. 07/699,406 filed concurrently herewith by Snyder et al.entitled "Tube Plug and Method for Plugging a Tube" and assigned to theassignee of the present invention. The tube plug for plugging a tube toprevent flow through the tube comprises a shell, an expander member,bolt means to seal the chamber defined by the shell, and locking meansfor securing the shell, bolt means and locking means together. The boltmeans reduces the possibility of residual stresses within the plug wall.However, utilization of the locking means requires the additional stepsof threading the locking means into the shell and of crimping thelocking means into the bolt means.

Therefore, what is needed is a tube plug and method for installing atube plug that automatically locks or fastens together the plurality ofmembers comprising the tube plug by the installation of the bolt meansinto the shell of the tube plug.

SUMMARY OF THE INVENTION

A fastener means for fastening a plurality of members together, such asthe plurality of members comprising a tube plug, for preventing the flowof fluid through the opening or tube, such as a nuclear steam generatortube, comprises locking means for automatically locking or fasteningtogether the plurality of members comprising the tube plug, during theinstallation of the tube plug into the tube. In some forms of theinvention, the tube plug comprises a first member, such as a shell,having a bore at least partially therein, a second member, such as abolt means, disposed in the bore of the first member, and locking meanshaving a deformable tab portion. The deformable tab portion may have anundercut positioned so that when the second member is installed withinthe first member, a first surface of the undercut is bent toward asecond surface of the undercut thereby plastically deforming the tabportion into a recess in at least one of the first and second membersfor securing the first and second members together. The tube plug mayalso comprise an expander member having threads with a different pitchsize than the threads of the locking means thereby providing anadditional locking or fastening feature of the tube plug.

A method for plugging the opening in the solid member, such as a tube,comprises the steps of installing the shell within the opening or tubeand plastically deforming the tab portion of the locking means into arecess by bending the first surface of the undercut of the tab portiontoward the second surface of the undercut as the bolt means is disposedin the shell of the tube plug for securing together the shell, the boltmeans, and the locking means to prevent fluid flow through the openingin the solid member or through the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the invention, it isbelieved the invention will be better understood from the followingdescription, taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a schematic illustration of a steam generator in partialvertical section with parts removed for clarity and also shows two steamgenerator tubes, one of the tubes having tube plugs disposed in the openends of the tube;

FIG. 2 is an exploded view and partial vertical section of a tube plugcomprising one embodiment of this invention;

FIG. 3 is an isometric view of the locking cup of FIG. 2 having acastellated tab portion;

FIG. 4 is a partial vertical section of the tube plug of FIG. 2 havingbolt means partially installed within a shell of the tube plug, andhaving the locking cup of FIG. 3 advancing along the bolt means;

FIG. 5 is a partial vertical section of the tube plug illustrated inFIGS. 2-4 having the bolt means and locking cup of FIG. 3 fullyinstalled within the shell of the tube plug;

FIG. 6 is an isometric view of an alternative embodiment of the lockingcup employable with the embodiment of FIG. 8 having a castellated tabportion and one or more pin receiving openings;

FIG. 7 is an isometric view of a pin employable with the locking cup ofFIG. 6;

FIG. 8 is a partial vertical section of an alternative embodiment of thetube plug having common parts removed for clarity and having the boltmeans and locking cup of FIG. 6 partially installed within the shell ofthe tube plug;

FIG. 9 is a partial vertical section of the tube plug illustrated inFIG. 8 having the bolt means and locking cup of FIG. 6 fully installedwithin the shell of the tube plug;

FIG. 10 is an isometric view of still another alternative embodiment ofthe locking cup employable with the embodiment of FIG. 12 having acastellated tab portion and one or more pin receiving openings;

FIG. 11 is an isometric view of a pin employable with the locking cup ofFIG. 10;

FIG. 12 is a partial vertical section of still another alternativeembodiment of the tube plug having common parts removed for clarity andhaving the bolt means and locking cup of FIG. 10 partially installedwithin the shell of the tube plug;

FIG. 13 is a partial vertical section of the tube plug illustrated inFIG. 12 having the bolt means and locking cup of FIG. 10 fully installedwithin the shell of the tube plug;

FIG. 14 is a partial vertical section of still another alternativeembodiment of the tube plug having common parts removed for clarity andhaving the bolt means integrally formed with the locking means andpartially installed within the shell of the tube plug;

FIG. 15 is a partial vertical section of the tube plug illustrated inFIG. 14 having the bolt means fully installed within the shell of thetube plug; and

FIG. 16 is a sectional view along line XVI-XVI of FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention described herein provides a fastener means for fastening aplurality of members together, such as the plurality of members whichform a tube plug, and method for plugging an opening in a solid member,which may be a tube, e.g. a nuclear steam generator tube, capable ofautomatically securing together the plurality of members comprising thetube plug, during the installation of the tube plug into the tube forpreventing the flow of fluid through the tube.

Referring to FIG. 1, steam generator 10 is schematically shown having aplurality of tubes 20 (only two of which are shown) disposed therein.One of the tubes 20, for example a tube 22 having an inner wall 24, mayhave become degraded after extended service due to vibration or primarywater stress corrosion cracking. Tube 22 may have a crack therethroughwhich will allow the commingling of the radioactive primary fluid intube 22 with the nonradioactive secondary fluid outside tube 22. Toprevent any such fluid commingling, steam generator 10 is taken out ofservice in a manner well known in the art and a tube plug 40 is disposedin both open ends of tube 22 for plugging the degraded tube 22. Aftertube 22 is plugged, steam generator 10 is returned to service. Tube plug40 prevents the flow of primary fluid through tube 22. However, thestress corrosion cracking which may have caused tube 22 to degrade mayalso affect tube plug 40 and thus cause tube plug 40 to likewisedegrade.

Referring to FIG. 2, a fastener means for securing a plurality ofmembers together is referred to generally as 44. As an example, thefastener means 44 fastens together the plurality of members comprisingthe tube plug 40, such as a first member or shell 52, an expander member54, a second member or bolt member, such as bolt means 56, and lockingmeans, such as the locking cup 58.

Referring to FIGS. 2-5, shell 52 is a substantially cylindrical membermanufactured from a metal, such as Inconel 600. The metal Inconel is analloy composed substantially of nickel, chromium, and iron and a traceamount of cobalt. Shell 52 has a conical inner surface 60 of an outerwall 62, which has a larger diameter at a closed end 64 of shell 52 anda smaller diameter at an open end 66 of shell 52 and a bore 68 at leastpartially therethrough. The closed end 64, open end 66 and outer wall 62define a chamber 70 in the shell 52. Disposed in chamber 70 is theexpander member 54, which may have a threaded cylindrical bore 72therethrough, for expanding the outer wall 62 of the shell 52 intosealing engagement with the inner wall 24 of tube 22 for plugging tube22. Inner surface 60 is formed such that expander member 54 is capturedwithin shell 52 so that movement of expander member 54 relative to innersurface 60 causes shell 52 to expand without allowing expander member 54to be removed from shell 52.

Shell 52 has a threaded cylindrical skirt portion 74 near open end 66,which has a diameter larger than the smallest diameter of inner surface60 of outer wall 62 for allowing an apparatus (not shown), such as atool for manipulating the expander member 54, to be threadedly engagedin the skirt portion or to be inserted through the threaded skirtportion 74 and into chamber 70. The skirt portion 74 has inside diameterthreads 75 for threadedly engaging the locking cup 58. The skirt portion74 also has a recess 76 positioned adjacent to and inward of the inwardend 77 of the inside diameter threads 75 of the skirt portion 74 forproviding thread relief to the inside diameter threads 75.

Shell 52 also has a substantially uniform wall thickness in the portionof the shell 52 that is expanded by expander member 54. A plurality ofouter lands 78 may be integrally formed on the outer surface 79 of shell52 in a manner such that the height of each land 78 increases fromclosed end 64 to open end 66 while the outer surfaces of all lands 78are maintained at approximately the same external diameter and while thewall thickness of shell 52 remains substantially constant throughout theportion of shell 52 where the lands 78 are located. The lands 78 mayprovide an enhanced seal between the shell 52 and the tube 22. Shell 52is also constructed such that the skirt portion 74 near the open end 66has a thicker wall section than the remainder of the shell 52 to providestability in extracting tube plug 40.

Prior to the completion of manufacture of the shell 52, the expandermember 54 is installed through the open end 66 of the shell 52 and intothe chamber 70 of the shell 52. Then, the shell 52 is swaged so that theexpander member 54 is captured within the shell 52.

Still referring to FIGS. 2-5, the expander member 54 may be manufacturedfrom a hardenable metal, such as Carpenter 455 and may be formed suchthat it has a leading end 80, which has a tangentially blended radiusthat minimizes "plowing" or pushing metal ahead of expander member 54when expander member 54 is pulled through shell 52. Expander member 54may also have a polished exterior surface that enhances its movementrelative to shell 52. Expander member 54 also has a trailing edge 82,which is formed to have a sharp edge such that it provides aself-locking mechanism. While the sharp edge feature of trailing edge 82retains expander member 54 from moving toward closed end 64 of shell 52,thereby preventing inadvertent diametral contraction of shell 52, theconstruction of expander member 54 is such that the sharp edge featureof trailing edge 82 does not prevent expander member 54 from beingpushed toward closed end 64 by a plug removal tool (not shown).

Expander member 54 is also provided with a conical outer surface 84 thatis arranged such that its outside diameter is smaller near leading end80 and larger near trailing edge 82. The shape of outer surface 84provides a mechanism for expanding shell 52 when expander member 54 ismoved relative to shell 52. Expander member 54 also has inside diameterthreads 86, which may be used for gripping a plug installation tool (notshown) during the expansion process and can be used to engage the boltmeans 56. As described hereinabove, the shell 52 and expander member 54may be of the type disclosed in U.S. Pat. No. 4,390,042 issued Jun. 28,1983 to Kucherer et al. entitled "Tube Plug" and assigned to theassignee of the present invention.

Still referring to FIGS. 2-5, the bolt means 56 has an outward endportion 90, an inward end portion 92, and a taper 93 positioned betweenthe outward end portion 90 and the inward end portion 92. When disposedthrough the open end 66 of the shell 52, the outward end portion 90 isdefined as that end portion of bolt means 56 nearer open 66 of the shell52 and the inward end portion 92 is defined as that end portion of boltmeans 56 nearer closed end 64 of the shell 52. The inward end portion 92may have outside diameter threads 94 corresponding to inside diameterthreads 86 of the expander member 54 for threaded engagement of the boltmeans 56 and the expander member 54. Bolt means 56 may be manufacturedfrom a metal, such as Inconel 690, for resisting stress corrosioncracking.

Bolt means 56 has a substantially circular flange 96 integrally attachedto the outward end portion 90. The flange 96 extends radially outwardfrom the outward end portion 90 of the bolt means 56 and across the openend 66 of the shell 52 for closing the open end 66, and thereby sealingthe chamber 70 defined by the shell 52. The flange 96 may also functionas a means for preventing over insertion of the bolt means 56 into shell52 because flange 96 will abut open end 66 when bolt means 56 issuitably inserted in shell 52. The bolt means 56 has a circumferentialrecess 98 positioned near and adjacent to the flange 96. Recess 98 andflange 96 have a common surface, referred to as surface 99. The outwardend portion 90 of bolt means 56 has a cavity 100, such as a hexagonalhole, for receiving an apparatus (not shown) capable of inserting thebolt means 56 into and retrieving bolt means 56 from the-shell 52 andthe expander member 54. The outward end portion 90 of the bolt means 56has a larger diameter than the inward end portion 92 of the bolt means56 for expanding the locking cup 58 into the skirt portion 74 of theshell 52 during installation of the bolt means 56 and of the locking cup58 into the shell 52. Because the exact position of the expander member54 within the shell 52 may not be known, the length of the bolt means 56should be sufficient for the outside diameter threads 94 to engage withthe inside diameter threads 86 of any installed expander member 54.

By fully installing the bolt means 56 into the shell 52, fluid isprevented from corrosively attacking the inner surface 60 of the shell52. Also, the bolt means 56 occupies space within the chamber 70,thereby reducing the liquid volume within the chamber 70 so that anystored energy in the chamber 70 is minimized. Sealing the chamber 70 andreducing the liquid volume within the chamber 70 provides a tube plug 40having reduced susceptibility to stress corrosion cracking.

Still referring to FIGS. 2-5, the locking cup 58 is an annular memberhaving a outward open end 102, an inward open end 104, and a wall 106.Wall 106 may have outside diameter threads 108 between the outward openend 102 and the inward open end 104 corresponding to the inside diameterthreads 86 of the skirt portion 74 of the shell 52 for threadedengagement of the locking cup 58 and the shell 52. The inside diameterthreads 75 of the shell 52 and the outside diameter threads 108 of thelocking cup 58 have a larger pitch than the inside diameter threads 86of the expander member 54 and the outside diameter threads 94 of thebolt means 56 for enabling the locking cup 58 to advance faster into theshell 52 than the bolt means 56 advances into the expander member 54.The difference in pitch size also provides an additional locking effectfor the bolt means 56, locking cup 58, and shell 52. The inward open end104 has a tapered internal diameter 109 which expands, duringinstallation of the locking cup 58 and the bolt means 56 into the shell52, as the locking cup 58 progresses along the bolt means 56 from theinward end portion 92 toward the outward end portion 90, to engage therecess 76 in the skirt portion 74 of the shell 52. Once expanded, thecombined diameter of the outward end portion 90 of the bolt means 56 andof the locking cup 58 is greater than the internal diameter of theinside diameter threads 75 of the skirt portion 74, thereby restrictingremoval of the bolt means 56 and of the locking cup 58 as a unit.

Referring to FIG. 3, locking cup 58 further comprises a deformable tabportion 110, positioned at the outward open end 102 of the locking cup58, for engagement with the bolt means 56 for securing together the boltmeans 56, the locking cup 58, and the shell 52. The tab portion 110 is aseries of slits 111 in the tab portion 110 and a series of castellatedtabs 112 for relieving the hoop stress in the tab portion 110 duringdeformation. The series of castellated tabs 112 may be a series ofprojecting tabs integrally formed on the tab portion 110. The tabportion 110 has an undercut 113 on the inside diameter 114 of the tabportion 110 for providing flexibility to enable the tab portion 110 tobe deformed. The tab portion also has an end 115. The tab portion 110 isoriginally in the straight position as illustrated in FIG. 4, whichenables the locking cup 58 to be slid onto the inward end portion 92 ofthe bolt means 56 and toward the outward end portion 90 of the boltmeans 56 until the locking cup 58 tightly fits onto the taper 93 andonto the outward end portion 90 of the bolt means 56. The tab portion110, which may be manufactured from a deformable metal, such as Inconel690, is deformed so that a first surface 116 of the undercut 113 is benttoward a second surface 118 of the undercut 113 and is in a position asillustrated in FIGS. 4 and 5. The plastically deformed tab portion 110will retain this bent position with minimal spring-back to the straightposition.

The initial length of the locking cup 58 may be longer than the internalclearance between the flange 96 of the bolt means 56 and the recess 76of the skirt portion 74. During installation of the bolt means 56, thefrictional fit between the locking cup 58 and the bolt means 56 willcause the locking cup 58 to thread into the skirt portion 74 of theshell 52. As the bolt means 56 is installed, due to the difference ofpitch between the locking cup 58 and the bolt means 56 and due to thelonger initial length of the locking cup 58, the locking cup 58 willseat in the recess 76 prior to the flange 96 abutting the shell 52. Asthe bolt means 56 and the locking cup 58 continue to thread into theshell 52, the flange 96 or surface 99 abuts an end 115 of tab portion110 and plastically deforms the tab portion 110 into the recess 98 ofthe bolt means 56 to provide an interference of the tab portion 110 ofthe locking cup 58 with the recess 98 of the bolt means 56 for fasteningor locking the bolt means 56 and the locking cup 58 together. Thelocking cup 58 also prevents inadvertent backward movement of the boltmeans 56 relative to the shell 52. The tab portion 110 is sized forknown forces such that the torque required to plastically deform the tabportion 110 from the recess 98 for removal of the bolt means 56 and thelocking cup 58 is higher than the torque expected to be applied to thebolt means 56 during service of the steam generator. By planning thesize of the tab portion 110, if the tube plug 40 needs to be removedfrom the tube 22, the tube plug 40 may be efficiently removed from thetube 22.

By utilizing locking means, such as the locking cup 58, the plurality ofmembers comprising the tube plug 40 are automatically locked or fastenedtogether by the installation of the bolt means 56 into the shell 52. Bylocking or fastening the members together, the chamber 70 remains sealedto prevent fluid from entering the chamber 70 and corrosively attackingthe inner surface 60 of the shell 52. The locking or fastening featurealso prevents a separation of the members, which may result in looseparts moving throughout the steam generator.

For the various embodiments of this invention, the same referencecharacters will be used to designate like parts. In addition, likefunctions and like interactions of parts among the various embodimentsof this invention will not be repeated for each embodiment. In theembodiments of FIGS. 6-9, FIGS. 10-13, and FIGS. 14-16, certain parts ofthe tube plug 40 have been left out of the drawings as these parts areduplicates of corresponding parts of the tube plug 40 in FIGS. 2-5.Alternative embodiments of this invention comprise tube plug 40employing various locking means.

Referring to FIGS. 6-9, an alternative embodiment of the locking cup 58as illustrated in FIGS. 2-5 is a locking cup 119 having like parts aslocking cup 58 and additionally having one or more openings 120positioned near the inward open end 104 of wall 106. One or more pins122 sized to fit within the openings 120 may be positioned within theopenings 120 to provide a pressure fit between the pins 122 and thelocking cup 119.

In addition to functioning similarity to the embodiment illustrated inFIGS. 2-5, as the locking cup 119 is installed, the pins 122 have aninclined surface 124 (as shown), which enables the pins 122 to slidealong the taper 93 of the bolt means 56 until the pins 122 are forcedoutward by the taper 93 to engage in the recess 76 positioned adjacentto the inside diameter threads 75 of the skirt portion 74 of the shell52. The engagement of the pins 122 with the recess 76 provides aninterference of the pins 122 with the inside diameter threads 75 of theskirt portion 74 of the shell 52 for locking or fastening the bolt means56 and the shell 52. The inclined surface 124 of the locking cup 119 hasa first edge 126 at one end for enabling the pins 122 to penetrate adistance into the bolt means 56 for providing an interference betweenthe pins 122 and the bolt means 56. By utilizing the pins 122, the wall106 of the locking cup 119 need not comprise the outside diameterthreads 108 nor the tab portion 110. Although the pins 122 may fasten orlock the bolt means 56, the locking cup 119, and the shell 52, it ispreferable to utilize the outside diameter threads 108 and the tabportion 110 for providing an additional locking or fastening feature.The pins 122 may be manufactured from a metal, such as Inconel 718,which is harder than the metal used to manufacture the tab portion 110,to provide a stronger locking feature than the locking feature of thetab portion 110.

Referring to FIGS. 10-13 and using the same reference characters todefine like parts, an alternative embodiment of the locking cup 119 asillustrated in FIGS. 6-9 may be locking cup 129 having like parts aslocking cup 119 and additionally having one or more openings 130positioned near the outward open end 102 of wall 106. One or more pins132 sized to fit within the openings 130 are positioned within theopenings 130 to provide a pressure fit between the pins 132 and thelocking cup 129. In addition to functioning similarly to the embodimentillustrated in FIGS. 6-9, as the locking cup 129 is installed, the pins132 may be forced to be positioned in the recess 98 of the bolt means 56utilizing a sloped counterbore 134 positioned at the open end 66 of theshell 52. The locking cup 129 also has a collapsible section 135positioned between the outward open end 102 and the inward open end 104of the locking cup 129 to permit engagement of the pins 122 prior tocontact of the pins 132 with the shell 52. The pins 132 have a surface136 with a second edge 137 for enabling the pins 132 to penetrate adistance into the shell 52 for providing an interference between thepins 132 and the shell 52. By utilizing the of pins 122 and the pins132, the wall 106 of the locking Cup 129 need not comprise the outsidediameter threads 108 nor the tab portion 110. Although the pins 122 andpins 132 fasten or lock the bolt means 56, the locking cup 129, and theshell 52, it is preferable to utilize the outside diameter threads 108and the tab portion 110 for providing an additional locking or fasteningfeature. The pins 132 may be manufactured from a metal, such as Inconel718, which is harder than the metal used to manufacture the tab portion110, to provide a stronger locking feature than the locking feature ofthe tab portion 110.

Referring to FIGS. 14-16 and using the same reference characters todefine like parts, an alternative embodiment of the tube plug 40 maycomprise of the bolt means 56 integrally formed with the locking means,such as locking means 140. The bolt means 56 is disposed in the open end66 of the shell 52. The bolt means 56 has a flange 96 extendingoutwardly from the outward end portion 90 of the bolt means 56 andacross the open end 66 of the shell 52. A recess 98 may be positionednear the flange 96 to provide flexibility to the flange 96 for enablingthe flange 96 to abut against the shell 52 for sealing engagement of theshell 52 and the bolt means 56. A deformable tab portion 110 may beintegrally formed with the bolt means 56 and has an undercut 113 forproviding flexibility to enable the tab portion 110 to be deformed.Referring to FIG. 16, the tab portion 110 has a series of slits 111 inthe tab portion 110 and a series of castellated tabs 112 for relievingthe hoop stress in the tab portion 110 during deformation. The series ofcastellated tabs 112 may be a series of projecting tabs integrallyformed on the tab portion 110. The deformable tab portion 110 ispositioned so that when the bolt means 56 is installed within the tubeplug 40, the deformable tab portion 110 will engage in the recess 76 ofthe shell 52. The tab portion 110 is originally in the straight positionas illustrated in FIG. 14, which enables the bolt means 56 to be slidinto the shell 52. The tab portion 110 is deformed so that the firstsurface 116 of the undercut 113 is bent toward the second surface 118 ofthe undercut 113 and is in a position as illustrated in FIG. 15.

Referring to FIG. 14, because the initial length between the end 115 ofthe tab portion 110 and the flange 96 is longer than the internalclearance between the flange 96 and the recess 76, during installationof the bolt means 56, the surface 142 of the recess 76 abuts end 115 ofthe tab portion 110 and plastically deforms tab portion 110 into therecess 76 to provide an interference of the tab portion 110 with therecess 76 for fastening or locking the bolt means 56 and the shell 52together. A groove 144 may be positioned near the deformable tab portion110 and between the recess 98 and the inward end portion 92 of the boltmeans 56 to provide flexibility to the tab portion 110 for enabling thetab portion 110 to be deformed into the recess 76 of the shell 52. Theinward end portion 92 of the bolt means 56 has outside diameter threads94 for threaded engagement with the inside diameter threads 95 of theexpander member 54 for sealing the chamber 70 defined by the shell 52,and for locking or fastening together the shell 52, the expander member54, the bolt means 56, and the locking means 140

OPERATION

Referring again to FIGS. 2 and 3, the shell 52 and the expander member54 may be positioned within the tube 22, as described in U.S. Pat. No.4,390,042 issued Jun. 28, 1983 to Kucherer et al. entitled "Tube Plug",and assigned to the assignee of the present invention. Locking cup 58 isslid onto the inward end portion 92 of the bolt means 56 and toward thetaper 93 and the outward end portion 90 of the bolt means 56 until thelocking cup 58 tightly fits onto the outward end portion 90 of the boltmeans 56. An installation tool (not shown) is inserted into the cavity100 of the bolt means 56 to install the bolt means 56 and locking cup 58into the shell 52. The installation tool (not shown) provides a torquesufficient to deform the locking cup 58 into position and sufficient toresult in a preload in the tube plug 40 to prevent significant leakageof fluid into the chamber 70 of the shell 52 through the metal-to-metalabutment of the flange 96 and shell 52 and through the metal-to-metalabutment of the tab portion 110 and the recess 98. The torque appliedalso is sufficient to prevent loosening of the tube plug 40 while thetube plug 40 is in service and sufficient to keep a compressive load onthe shell 52 for reducing the possibility of a separation of the shell52 due to stress corrosion cracking.

Referring again to FIGS. 2 and 4, the bolt means 56 with the locking cup58 fit onto the taper 93 is threaded into the expander member 54positioned within the shell 52. As the bolt means 56 is threaded intothe expander member 54, the frictional fit between the locking cup 58and the bolt means 56 causes the locking cup 58 to advance along thetaper 93 of the bolt means 56 and toward the outward end portion 90 ofthe bolt means 56, where the locking cup 58 threads into the skirtportion 74 of the shell 52. The locking cup 58 may thread faster intothe shell 52 than the bolt means 56 threads into the expander member 54due to the difference in pitch size of the inside diameter threads 86 ofthe expander member 54 and the inside diameter threads 75 of the skirtportion 74 of the shell 52.

Referring again to FIGS. 4 and 5, the inward open end 104 of the lockingcup 58 seats in the recess 76 of the shell 52 prior to the flange 96 ofthe bolt means 56 abutting the shell 52, due to the initial longerlength of the locking cup 58 as compared to the internal clearancebetween the flange 96 and the recess 76. After the seating of the inwardopen end 104 and as the bolt means 56 continues to thread into theexpander member 54, the flange 96 or surface 99 abuts end 115 of tabportion 110 and plastically deforms the tab portion 110 of the lockingcup 58 into the recess 98 of the bolt means 56 by bending the firstsurface 116 of the undercut 113 toward the second surface 118 of theundercut 113. After the tab portion 110 engages the recess 98, theflange 96 abuts the shell 52. The recess 98 allows flexibility for theflange 96 to sealingly abut the shell 52 for sealing the chamber 70 ofthe shell 52. The threaded engagement of the locking cup 58 and theshell 52, the threaded engagement of the expander member 54 and the boltmeans 56, and the engagement of the tab portion 110 of the locking cup58 and the recess 98 of the bolt means 56 locks or fastens the shell 52,the expander member 54, the bolt means 56, and the locking cup 58together for providing a tube plug 40 to prevent fluid flow through tube22.

Referring again to FIGS. 6-9, in addition to the interaction of theparts as described above, the one or more pins 122 are positioned withinthe one or more openings 120 in the locking cup 119 to provide apressure fit between the pins 122 and the locking cup 119. As thelocking cup 119 is threaded into the skirt portion 74 of the shell 52,the pins 122 slide along the taper 93 of the bolt means 56 until thepins 122 are forced outward by the taper 93 to engage in the recess 76of the inside diameter threads 75 of the skirt portion 74 of the shell52. The pins 122 may penetrate a distance into the bolt means 56 forproviding an additional locking or fastening feature.

Referring again to FIGS. 10-13, in addition to the interaction of theparts as described above, one or more pins 132 are positioned within oneor more openings 130 in the locking cup 129 to provide a pressure fitbetween the pins 132 and the locking cup 129. As the locking cup 129 isthreaded into the skirt portion 74 of the shell 52, the pins 132 engagein the recess 98 of the bolt means 56. The pins 132 may penetrate adistance into the sloped counterbore 134 of the shell 52 for providingan additional locking or fastening feature.

Referring again to FIGS. 14-16, the bolt means 56 is threaded into theexpander member 54 by utilizing an installation tool (not shown)inserted into the cavity 100. As the bolt means 56 is threaded into theexpander member 54, the end 115 of the tab portion 110 of the lockingmeans 140 abuts the surface 142 of recess 76 of the shell 52 prior tothe flange 96 of the bolt means 56 abutting the shell 52. After the tabportion 110 abuts the surface 142 of the recess 76 and as the bolt means56 continues to thread into the expander member 54, the tab portion 110is plastically deformed by the surface 142 of the recess 76 bending thefirst surface 116 of the undercut 113 toward the second surface 118 ofthe undercut 113 to engage the tab portion 110 in the recess 76. Therecess 98 provides the flexibility for a sealingly abutment between theflange 96 and the shell 52 and groove 144 provides the flexibility for asealingly abutment between the tab portion 110 and the shell 52 to sealthe chamber 70 of the shell 52. The installation tool (not shown)provides a torque sufficient to deform the locking means 140 intoposition and sufficient to result in a preload in the tube plug 40 toprevent significant leakage of fluid into the chamber 70 of the shell 52through the metal-to-metal abutment of the flange 96 and shell 52 andthrough the metal-to-metal abutment of the tab portion 110 and therecess 76. The threaded engagement of the bolt means 56 and the expandermember 54, and the engagement of the tab portion 110 of the lockingmeans 140 and the recess 76 of the shell 52 locks or fastens the shell52, the bolt means 56, and the locking means 140 together for providinga tube plug 40 to prevent fluid flow through tube 22.

Referring again to FIGS. 2-16, to remove the tube plug 40 from the tube22, the bolt means 56 must be removed from the shell 52 and then thetube plug 40 may be removed by methods well known in the art. To removethe bolt means 56 from the shell 52, a removal tool (not shown) isinserted into the cavity 100 in the flange 96 and provides a torquesufficient to plastically deform the tab portion 110 so that the tabportion 110 disengages from the recess 76 or the recess 98. The torquemust also be sufficient to overcome the resistance from the differencein the pitch sizes of the threads 75 of the skirt portion 74 of theshell 52 and of the threads 86 of the expander member 54. The torquemust also be sufficient to disengage the one or more pins 122 from therecess 76 and the one or more of pins 132 from the recess 98.

Therefore, the invention provides a tube plug that automatically locksor fastens together the plurality of members comprising the tube plug asthe members of the tube plug are installed within the tube, a locking orfastening means that locks or fastens the bolt means to the shell at anyelevation of the shell within the tube, and a tube plug that has areduced susceptibility to stress corrosion cracking due to the reductionof primary fluid within the chamber of the tube plug.

We claim:
 1. A tube plug for plugging a tube, comprising:a shell havinga closed end, an open end, and an outer wall defining a chamber in saidshell and having inside diameter threads positioned near said open end;a bolt member disposed in said open end of said shell; a least one ofsaid shell and said bolt member having a recess therein which faces theother of said shell and said bolt member; and means for locking saidshell and said bolt member together, said locking means having adeformable tab portion therein, said tab portion having an undercutincluding a first surface and a second surface positioned between an endof said tab portion and the remainder of said means for locking, atleast one of said shell and said bolt member having means for forcingsaid first surface of said undercut to bend toward said second surfaceof said undercut, so that when said bolt member is installed within saidshell, said means for forcing on one of said shell and said bolt memberforces said first surface of said undercut to bend toward said secondsurface of said undercut, said tab portion being engageable with therecess and plastically deformable to reduce said undercut by movement ofsaid tab portion into said recess for securing said shell, said boltmember, and said means for locking together for preventing fluid flowthrough said tube.
 2. The tube plug according to claim 1 wherein saidmeans for locking is integrally formed with said bolt member.
 3. Thetube plug according to claim 2 wherein said recess is positioned betweenopposite ends of said shell for forcing said first surface of saidundercut to bend toward said second surface of said undercut, as saidbolt member is installed within said shell, for engaging said tabportion in said recess for securing said shell, said bolt member, andsaid means for locking together.
 4. The tube plug according to claim 1wherein said bolt member further comprises a flange extending radiallyoutward from an end of said bolt member and across an open end of saidshell for sealing said chamber of said shell.
 5. The tube plug accordingto claim 4 wherein said for locking is a locking cup disposed in saidbore of said shell having said tab portion at one end and having outsidediameter threads for threadedly engaging said inside diameter threads ofsaid shell for securing said shell, said bolt member, and said lockingcup together.
 6. The tube plug according to claim 5 wherein said recessis positioned adjacent to said flange for engaging said tab portion ofsaid locking cup in said recess of said bolt member as said flangeforces said first surface of said undercut to bend toward said secondsurface of said undercut, as said bolt member and said locking cup areinstalled within said shell, for securing said shell, said bolt member,and said locking cup together.
 7. The tube plug according to claim 1wherein said tube plug further comprises an expander member, having abore therethrough with inside diameter threads, disposed in said chamberof said shell for expanding said outer wall of said shell into sealingengagement when installed in a tube.
 8. The tube plug according to claim7 wherein said inside diameter threads of said expander member and saidoutside diameter threads of said bolt member have a different pitch thanthe pitch of said inside diameter threads of said shell and said outsidediameter threads of said means for locking for providing an additionalfastening feature to secure said shell, said bolt member, said means forlocking, and said expander member together.
 9. The tube plug accordingto claim 1 wherein said tab portion of said means for locking is aseries of castellated tabs and slits for reducing the hoop stresscreated during the plastic deformation of said tab portion into saidrecess.
 10. The tube plug according to claim 5 wherein said locking cuphas at least one opening through a wall of said locking cup andpositioned near said inward open end of said locking cup and furthercomprises at least one pin sized to fit as a pressure fit within saidopening for engaging said recess of said shell for providing aninterference between said pin and said inside diameter threads of saidshell for providing an additional fastening feature for securing saidshell, said bolt member, and said locking cup together.
 11. The tubeplug according to claim 5 wherein said locking cup has at least oneopening through a wall of said locking cup and positioned near saidoutward open end of said locking cup and further comprises at least onepin sized to fit as a pressure fit within said opening for engaging saidrecess of said bolt member for providing an interference between saidpin and a counterbore of said shell for providing as additionalfastening feature for securing said shell, said bolt member, and saidlocking cup together.
 12. The tube plug according to claim 10 whereinsaid pin comprises an inclined surface having an edge, said edgeprotruding into said bolt member for providing an additional fasteningfeature for securing said shell, said bolt member, and said locking cuptogether.